1. Field of the Invention
This invention relates to quaternary 2-alkylimidazolinium salts, to a process for their production and to their use.
2. Discussion of Related Art
It has long been known that quaternary tetraalkylammonium compounds containing two long-chain alkyl radicals and two short-chain alkyl radicals, for example, two C.sub.16 -C.sub.18 alkyl radicals and two methyl radicals, impart a soft feel to washed fabrics when added to the final rinse of a washing process. These fabric softeners are widely used both in institutional laundries and also in domestic washing. It is assumed that these cationic quaternary ammonium compounds are readily absorbed onto the fabric substrate by virtue of their positive charge.
The most commonly used fabric softener of this type is distearyl dimethylammonium chloride (cf. S. Billenstein et al, J. Am. Oil Chem. Soc. 61 (1984), pp. 353 to 357). Although fabric softeners of this type show excellent softening properties, they are also attended by certain disadvantages. That is, the fabrics treated with them show reduced absorbency compared with untreated fabrics, which can be unpleasant to the user, for example in the case of articles of clothing worn in contact with the skin and in the case of terry towels. Fabric softeners of the afore-mentioned type often cannot be completely removed from the fabric during washing, so that, despite correct dosage, there is occasionally an accumulation of the softening agents which again results in reduced absorbency of the fabrics. Another serious disadvantage of such fabric softeners is their corrosive effect on metal surfaces caused by the chloride anion.
There has been no shortage of attempts to improve the properties of fabric softeners based on quaternary ammonium compounds. Thus, it is known from U.S. Pat. No. 3,636,114 that the absorbency of treated fabrics can be improved by using quaternary ammonium compounds containing two long-chain 2-hydroxyalkyl radicals. Quaternary ammonium compounds containing two long-chain 2-hydroxy-3-alkoxypropyl groups are known from U.S. Pat. Nos. 3,932,495; 3,972,855 and 4,104,175. German patent application No. 16 19 043 describes softeners which contain quaternary ammonium compounds having only one long alkyl radical and 3 short alkyl radicals, wherein the 3 short alkyl radicals may contain hydroxyl and ether groups. Dutch patent application No. 86/08958 and U.S. Pat. No. 3,591,405 describe quaternary ammonium compounds wherein the hydrophobic radicals are hydroxyalkyl groups or alkyl groups attached to the nitrogen by ethoxy groups. However, none of these attempted solutions was satisfactory either because the modified quaternary ammonium compounds are difficult to prepare and, accordingly, are unsuitable for practical application, or because the softening effect is too weak.
Accordingly, an object of the present invention is to provide new quaternary ammonium compounds which may readily be obtained from readily available starting materials. The new compounds are intended to leave the absorbency of the fabrics treated with them intact despite their favorable softening effect and to be completely removable during the washing of the fabrics. In addition, they are to have no corrosive effect on metal surfaces.